A welding method for a stop valve welding assembly line

Abstract

The application discloses a kind of welding methods of stop valve welding assembly line, it is related to stop valve processing method technical field, comprising the following steps, feeding, manual insertion copper pipe, dip soldering flux, cover protective cap, first preheating, second preheating, welding, air cooling, first gas cooling, second gas cooling, open protective cap, water cooling and discharging.The welding method with high degree of automation is used, the number of workers required for the present welding production line is reduced to 1.4 from 2, and the labor intensity of workers is reduced;The welding quality of the welding product obtained by the welding method is stable, the product scrap rate is low during the welding process, and the production cost of the stop valve is reduced.

Description

Technical Field

[0001] This invention relates to the technical field of gate valve processing methods, and in particular to a welding method for a gate valve welding production line. Background Technology

[0002] The shut-off valve is a crucial component of split-type air conditioners. Operating the valve stem closes the internal passage, connecting the outdoor and indoor units, and opening or closing the refrigerant circuit. It can also serve as a maintenance valve for vacuuming or refrigerant charging during maintenance. The manufacturing process of shut-off valves involves welding copper tubing to the valve's welded end. Currently, this welding process is performed manually in conjunction with a welding machine. Specifically, on a welding line, one worker manually applies flux to one end of the copper tubing, inserts it into the welded end of the shut-off valve, places the assembled valve on a welding fixture, and then attaches a protective cap to the other end of the copper tubing. The welding machine then automatically welds the valve. After welding and cooling, another worker manually removes the welded valve from the welding machine, removes the protective cap, performs a visual inspection, and neatly arranges the qualified shut-off valves in a product box, completing one cycle of the copper tubing welding process. Because the welding process between the copper pipe and the gate valve is carried out by a combination of manual labor and welding machine, at least two workers are required to work on one welding line, and the workers' labor intensity is high; the workers operate based on their personal experience, which leads to fluctuations in the quality of the welded products. Summary of the Invention

[0003] The purpose of this invention is to provide a welding method for a shut-off valve welding production line in order to solve the above-mentioned problems.

[0004] The present invention achieves the above objectives through the following technical solutions:

[0005] A welding method for a gate valve welding production line includes the following steps:

[0006] (1) Loading: The semi-finished stop valves are neatly placed in the turnover box. Multiple rows of stop valves can be placed in the turnover box. Then, the turnover box is placed on the first conveyor belt of the first workbench. When the first conveyor belt transports the turnover box to the vicinity of the first loading mechanism, it stops working. The first loading mechanism uses pneumatic grippers to pick up a row of stop valves from the turnover box on the first conveyor belt and then places them on the second conveyor belt. When the second conveyor belt transports the stop valves to the vicinity of the second loading mechanism, it stops working. At the same time, the material distribution mechanism on one side of the second conveyor belt uses pneumatic grippers to separate multiple stop valves on the second conveyor belt in sequence so that there is a certain gap between the stop valves. The adjustment mechanism on one side of the second conveyor belt uses the first cylinder to drive the round rod to move and straighten the position of the skewed stop valves on the second conveyor belt. The second loading mechanism uses pneumatic grippers to pick up the straightened stop valves on the second conveyor belt. Then, the servo motor drives the connecting rod to flip and send the stop valves to a set of placement rods of the rotating mechanism on the second workbench.

[0007] (2) Manual insertion of copper pipe: A worker near the placement box of the first workbench takes the copper pipe from the placement box and inserts it into the welding end of the stop valve on the placement rod of the rotating mechanism, which is conveyed by the second feeding mechanism.

[0008] (3) Apply flux, the rotating mechanism rotates and drives the stop valve with the copper tube inserted at the welding end in step (2) to enter the area below the flux application mechanism. The flux application mechanism works by using pneumatic grippers to pick up the stop valve, and then uses a lateral movement mechanism to move the stop valve to the top of the flux container. At this time, the second cylinder on the flux application mechanism works and drives the brush on the bracket, which is dipped in flux from the flux container, to move upward. The brush applies flux to the welding end of the stop valve. Then, the lateral movement mechanism drives the stop valve back, and the pneumatic grippers place the flux-coated stop valve back on the placement rod of the rotating mechanism.

[0009] (4) Cover the protective cap. The rotating mechanism rotates and drives the shut-off valve coated with flux in step (3) to enter the protective cap covering station. The first cylinder on the protective cap covering station works and drives the round rod to extend forward and push against the protective cap on the copper pipe, flipping the protective cap to cover the port of the copper pipe.

[0010] (5) First preheating, the rotating mechanism rotates and drives the stop valve with the protective cap in step (4) to enter the first preheating station. The heating gun in the first preheating station heats the welding end of the stop valve for a period of time.

[0011] (6) Secondary preheating: The rotating mechanism rotates to drive the shut-off valve that has been preheated once in step (5) into the second preheating station. The heating gun in the second preheating station heats the welded end of the shut-off valve for a period of time.

[0012] (7) Welding: The rotating mechanism rotates and drives the stop valve that has been preheated twice in step (6) to enter the welding station. The welding machine at the welding station welds the welding end of the stop valve so that the copper pipe is welded and fixed to the welding end of the stop valve.

[0013] (8) Air cooling: The rotating mechanism rotates and drives the shut-off valve that was welded in step (7) into the air cooling station, where it is naturally cooled for a period of time.

[0014] (9) First air cooling, the rotating mechanism rotates and drives the air-cooled shut-off valve in step (8) to enter the first air cooling station. The air nozzle on the first air cooling station blows air onto the welded end of the shut-off valve for a period of time to help it cool down.

[0015] (10) Secondary air cooling: The rotating mechanism rotates and drives the shut-off valve that has passed through the first air cooling in step (9) to enter the second air cooling station. The air nozzle on the second air cooling station blows air onto the welding end of the shut-off valve for a period of time to help it cool down.

[0016] (11) Open the protective cap. The rotating mechanism works and drives the shut-off valve that has been cooled twice in step (10) to enter the vicinity of the protective cap opening mechanism. The first cylinder on the protective cap opening mechanism works and drives the round rod to extend forward and push against the protective cap covering the copper pipe port, flipping the protective cap away from the copper pipe port.

[0017] (12) Water cooling, the rotating mechanism rotates to drive the stop valve of the copper pipe port protective cap in step (11) to enter the water cooling station. The nozzle on the water cooling station sprays cooling water onto the stop valve to help it cool, but do not let the cooling water come into contact with the welding end.

[0018] (13) Unloading: The rotating mechanism stops when the water-cooled shut-off valve from step (12) approaches the unloading mechanism. The unloading mechanism uses pneumatic grippers to pick up the water-cooled shut-off valve from step (12) on the placement rod of the rotating mechanism. Then, the shut-off valve is placed on the third conveyor belt. One assistant worker performs a visual inspection of the shut-off valve on the third conveyor belt and neatly arranges the qualified shut-off valves in the product box.

[0019] Preferably, in step (2), when the worker inserts the copper pipe into the welding end of the shut-off valve, it is necessary to ensure that the copper pipe is inserted into the bottom of the welding end.

[0020] Preferably, the flux in step (3) is an acid-free flux FB403L.

[0021] Preferably, in step (3), the flux is applied at a position of 0-10 mm above the copper tube on the mounting plate.

[0022] Preferably, the heating temperature for the first preheating in step (5) is 550-620°C and the heating time is 1.9-3.2s.

[0023] Preferably, the heating temperature for the secondary preheating in step (6) is 630-650°C and the heating time is 1.9-3.2s.

[0024] Preferably, in step (7), the distance between the wire feed nozzle of the welding machine and the copper tube is maintained at 10-15 mm.

[0025] Preferably, the welding temperature in step (7) is 650-740℃ and the welding time is 1.9-3.2s.

[0026] Preferably, the air cooling time in step (8) is 3.2 to 3.8 s; the temperature of the first air cooling in step (9) is 400 to 440 ℃ and the first air cooling time is 3.2 to 3.8 s; the temperature of the second air cooling in step (10) is 280 to 320 ℃ and the second air cooling time is 3.2 to 3.8 s; and the temperature of the water cooling in step (12) is 35 to 45 ℃ and the water cooling time is 3.2 to 3.8 s.

[0027] Preferably, straight copper tubes must undergo the processing steps in steps (4) and (11); bent copper tubes do not need to undergo the processing steps in steps (4) and (11).

[0028] The beneficial effects of the present invention are as follows: (1) The present invention adopts a highly automated welding method, which reduces the number of workers required for a welding production line from 2 to 1.4, and reduces the labor intensity of the workers; (2) The quality of the welded products obtained by the welding method is stable, the scrap rate of the products during the welding process is low, and the production cost of the gate valve is reduced; (3) The connection between different processes is close, reducing the intermediate transition time and improving the welding efficiency. Attached Figure Description

[0029] Figure 1 This is a perspective view of the overall structure of the present invention;

[0030] Figure 2 This is a perspective view of the loading and unloading mechanism of the present invention;

[0031] Figure 3 This is a perspective view of the material dispensing mechanism and the adjustment mechanism of the present invention;

[0032] Figure 4 This is a perspective view of the rotating mechanism of the present invention;

[0033] Figure 5 This is a perspective view of the shut-off valve of the present invention.

[0034] Explanation of reference numerals in the attached figures:

[0035] 11. First workbench; 111. Placement box; 12. Second workbench;

[0036] 21. First conveyor belt; 22. Second conveyor belt; 23. Third conveyor belt; 24. Rotating mechanism; 241. Placement rod;

[0037] 31. First feeding mechanism; 311. Pneumatic gripper; 32. Second feeding mechanism; 321. Servo motor; 322. Connecting rod; 33. Material distribution mechanism; 34. Adjustment mechanism; 341. First cylinder; 342. Round rod;

[0038] 4. Feeding mechanism;

[0039] 5. Turnover boxes;

[0040] 501. Flux application mechanism; 5011. Lateral movement mechanism; 5012. Flux container; 5013. Support; 5014. Second cylinder; 502. Protective cap application station; 503. First preheating station; 504. Second preheating station; 505. Welding station; 506. Air cooling station; 507. First air cooling station; 508. Second air cooling station; 509. Protective cap opening mechanism; 510. Water cooling station;

[0041] 6. Touchscreen;

[0042] 7. Gate valve; 71. Welded end; 72. Mounting plate; 721. Mounting hole; 73. Valve cap end; 74. Connecting pipe nut end; 75. Filling end;

[0043] 8. Copper pipes. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings:

[0045] like Figure 5 As shown, the stop valve 7 includes a two-way stop valve and a three-way stop valve. This invention can be used to weld both two-way and three-way stop valves. Taking the three-way stop valve as an example, one end of the stop valve 7 is set as a welding end 71, and a copper tube 8 can be inserted into the welding end 71. The copper tube 8 is fixedly connected to the welding end 71 by welding. A mounting plate 72 is fixedly set on the outer side of the stop valve 7 near the welding end 71. The mounting plate 72 has two symmetrically distributed mounting holes 721. The other end of the stop valve 7 is set as a valve cap end 73. A connecting pipe nut end 74 is set on one side of the stop valve 7, and a filling end 75 is set on the other side of the stop valve 7.

[0046] like Figure 1 , Figure 2 , Figure 3 and Figure 4As shown, the present invention provides a welding method for a gate valve welding production line, comprising the following steps: (1) feeding: the semi-finished gate valves 7 are neatly placed in the turnover box 5, and multiple rows of gate valves 7 can be placed in the turnover box 5. Then, the turnover box 5 is placed on the first conveyor belt 21 on the first workbench 11. When the first conveyor belt 21 transports the turnover box 5 to the vicinity of the first feeding mechanism 31, it stops working. The first feeding mechanism 31 works by using pneumatic grippers 311 to clamp a row of gate valves 7 from the turnover box 5 on the first conveyor belt 21 and then place them on the second conveyor belt 22. When the second conveyor belt 22 transports the gate valves 7 to the vicinity of the second feeding mechanism 32, it stops working. During operation, the material distribution mechanism 33 on one side of the second conveyor belt 22 uses pneumatic grippers 311 to separate multiple shut-off valves 7 on the second conveyor belt 22 in sequence, leaving a certain gap between the shut-off valves 7. The adjustment mechanism 34 on one side of the second conveyor belt 22 uses the first cylinder 341 to drive the round rod 342 to move and straighten the position of the skewed shut-off valves 7 on the second conveyor belt 22. The second feeding mechanism 32 uses pneumatic grippers 311 to clamp the straightened shut-off valves 7 on the second conveyor belt 22, and then uses the servo motor 321 to drive the connecting rod 322 to rotate and send the shut-off valves 7 to a set of placement rods 241 of the rotating mechanism 24 on the second worktable 12. (2) Manually inserting copper tube 8: A worker near the placement box 111 of the first workbench 11 takes copper tube 8 from the placement box 111 and inserts it into the welding end 71 of the stop valve 7, which is conveyed to the placement rod 241 of the rotating mechanism 24 by the second feeding mechanism 32. When inserting copper tube 8 into the welding end 71 of the stop valve 7, the worker needs to ensure that the copper tube 8 contacts the bottom of the welding end 71. (3) Apply flux. The rotating mechanism 24 rotates and drives the stop valve 7, which is connected to the copper tube 8 at the welding end 71 in step (2), to enter the area below the flux application mechanism 501. The flux application mechanism 501 works by using the pneumatic gripper 311 to clamp the stop valve 7, and then uses the transverse moving mechanism 5011 to move the stop valve 7 to the top of the flux container 5012. At this time, the second cylinder 5014 on the flux application mechanism 501 works and drives the brush on the bracket 5013, which is dipped in flux from the flux container 5012, to move upward. The brush applies flux to the welding end 71 of the stop valve 7. The flux is a non-acid-washing flux FB403L, and the position of the flux application is 0-10mm above the copper tube 8 on the mounting plate 72. Then, the lateral movement mechanism 5011 drives the shut-off valve 7 back, and the pneumatic gripper 311 places the flux-coated shut-off valve 7 back onto the placement rod 241 of the rotation mechanism 24. The lateral movement mechanism 5011 is a structure in which a servo motor drives a lead screw to rotate a nut, thereby enabling the pneumatic gripper 311 to move in the horizontal direction.(4) Cover with protective cap. The rotating mechanism 24 rotates and drives the stop valve 7, which has been coated with flux in step (3), to the protective cap covering station 502. The first cylinder 341 on the protective cap covering station 502 works and drives the round rod 342 to extend forward and push against the protective cap on the copper tube 8, flipping the protective cap to cover the port of the copper tube 8. (5) First preheating. The rotating mechanism 24 rotates and drives the stop valve 7, which has been covered with protective cap in step (4), to the first preheating station 503. The heating gun on the first preheating station 503 heats the welding end 71 of the stop valve 7 for a period of time. The heating temperature of the first preheating is 550~620℃ and the heating time is 1.9~3.2s. (6) Secondary preheating: The rotating mechanism 24 rotates to drive the shut-off valve 7, which has undergone secondary preheating in step (5), into the second preheating station 504. The heating gun on the second preheating station 504 heats the welding end 71 of the shut-off valve 7 for a period of time. The heating temperature of the secondary preheating is 630-650℃ and the heating time is 1.9-3.2s. (7) Welding: The rotating mechanism 24 rotates to drive the shut-off valve 7, which has undergone secondary preheating in step (6), into the welding station 505. The welding machine on the welding station 505 welds the welding end 71 of the shut-off valve 7 so that the copper tube 8 is welded and fixed to the welding end 71 of the shut-off valve 7. The distance between the wire feed nozzle of the welding machine and the copper tube 8 is maintained at 10-15mm. The welding temperature is 650-740℃ and the welding time is 1.9-3.2s. (8) Air cooling: The rotating mechanism 24 rotates to drive the shut-off valve 7, which has been welded in step (7), into the air cooling station 506 for natural cooling for a period of time, wherein the air cooling time is 3.2 to 3.8 seconds. (9) Primary air cooling: The rotating mechanism 24 rotates to drive the shut-off valve 7, which has been air cooled in step (8), into the first air cooling station 507. The air nozzle on the first air cooling station 507 blows air onto the welded end 71 of the shut-off valve 7 for a period of time to help it cool down. The temperature of the primary air cooling is 400 to 440°C, and the primary air cooling time is 3.2 to 3.8 seconds. (10) Secondary air cooling: The rotating mechanism 24 rotates to drive the shut-off valve 7, which has been air cooled in step (9), into the second air cooling station 508. The air nozzle on the second air cooling station 508 blows air onto the welded end 71 of the shut-off valve 7 for a period of time to help it cool down. The temperature of the secondary air cooling is 280 to 320°C, and the secondary air cooling time is 3.2 to 3.8 seconds.(11) Open the protective cap. The rotating mechanism 24 rotates and drives the shut-off valve 7, which has been cooled twice in step (10), to enter the vicinity of the protective cap opening mechanism 509. The first cylinder 341 on the protective cap opening mechanism 509 works and drives the round rod 342 to extend forward and push against the protective cap covering the copper pipe 8 port, flipping the protective cap off the copper pipe 8 port. (12) Water cooling. The rotating mechanism 24 rotates and drives the shut-off valve 7, which opened the protective cap at the copper pipe 8 port in step (11), to enter the water cooling station 510. The nozzle on the water cooling station 510 sprays cooling water onto the shut-off valve 7 to help it cool, but do not let the cooling water come into contact with the welding end 71. The water cooling temperature is 35-45℃ and the water cooling time is 3.2-3.8s. (13) Unloading: The rotating mechanism 24 rotates and drives the water-cooled shut-off valve 7 from step (12) to approach the unloading mechanism 4 and stops. The unloading mechanism 4 uses pneumatic grippers 311 to pick up the water-cooled shut-off valve 7 from the placement rod 241 of the rotating mechanism 24 from step (12), and then places the shut-off valve 7 on the third conveyor belt 23. One auxiliary worker performs a visual inspection of the shut-off valve 7 on the third conveyor belt 23 and neatly arranges the qualified shut-off valve 7 in the product box. When the auxiliary worker performs a visual inspection of the shut-off valve 7 on the third conveyor belt 23, he needs to visually inspect the weld seam of the welded end 71 of the shut-off valve 7. The weld seam should be smooth and firm, and there should be no pits, cracks, pores, incomplete penetration, or reverse welding or incorrect welding of the copper tube 8. The surface of the welded part should not be damaged and the inner surface should not be oxidized. Then, the qualified shut-off valve 7 is neatly arranged in the product box, and the defective products are placed in the defective product box. Among them, copper pipe 8 is divided into straight copper pipe and bent copper pipe. Straight copper pipe must be processed in steps (4) and (11); while bent copper pipe does not need to be processed in steps (4) and (11). The protective cap is placed on the end of copper pipe 8 by flipping to prevent impurities from entering the shut-off valve 7 during the welding process. Only straight copper pipe needs a protective cap, while bent copper pipe does not need a protective cap.

[0047] like Figure 1 As shown, a touch screen 6 is fixedly installed on the first workbench 11, through which the operating parameters of different mechanisms on the welding production line can be set. A placement box 111 for placing copper tubes 8 is fixedly installed on the first workbench 11 near the flux application mechanism 501. One worker on this welding production line is positioned near the placement box 111 for easy insertion of the copper tubes 8 from the placement box 111 into the welding end 71 of the shut-off valve 7 on the rotating mechanism 24. Before each use of the welding production line, the gas source, welding machine power supply, and automation equipment power supply must be turned on, and the "reset" button must be pressed for initialization.

[0048] After adopting the highly automated welding production line of this invention, only one worker is needed on one welding production line, and one assistant worker is needed for three welding production lines. According to statistics, the welding efficiency has been increased by 54.1%; the scrap rate of welded products is 0.59‰, which is lower than the existing scrap rate of 0.65‰.

[0049] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Those skilled in the art will understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the equivalents of the claims.

Claims

1. A method for welding gate valves using a gate valve welding production line, characterized in that: Includes the following steps: (1) Loading: The semi-finished stop valves are neatly placed in the turnover box. Multiple rows of stop valves are placed in the turnover box. Then the turnover box is placed on the first conveyor belt of the first workbench. When the first conveyor belt transports the turnover box to the vicinity of the first loading mechanism, it stops working. The first loading mechanism uses pneumatic grippers to pick up a row of stop valves from the turnover box on the first conveyor belt and then places them on the second conveyor belt. When the second conveyor belt transports the stop valves to the vicinity of the second loading mechanism, it stops working. At the same time, the material distribution mechanism on one side of the second conveyor belt uses pneumatic grippers to separate multiple stop valves on the second conveyor belt in sequence so that there is a certain gap between the stop valves. The adjustment mechanism on one side of the second conveyor belt uses the first cylinder to drive the round rod to move and straighten the position of the skewed stop valve on the second conveyor belt. The second loading mechanism uses pneumatic grippers to pick up the straightened stop valve on the second conveyor belt. Then, the servo motor drives the connecting rod to flip and send the stop valve to a set of placement rods of the rotating mechanism on the second workbench. (2) Manual insertion of copper pipe: A worker near the placement box of the first workbench takes the copper pipe from the placement box and inserts it into the welding end of the stop valve on the placement rod of the rotating mechanism, which is conveyed by the second feeding mechanism. (3) Apply flux, the rotating mechanism rotates and drives the stop valve with the copper tube inserted at the welding end in step (2) to enter the area below the flux application mechanism. The flux application mechanism works by using pneumatic grippers to pick up the stop valve, and then uses a lateral movement mechanism to move the stop valve to the top of the flux container. At this time, the second cylinder on the flux application mechanism works and drives the brush on the bracket, which is dipped in flux from the flux container, to move upward. The brush applies flux to the welding end of the stop valve. Then, the lateral movement mechanism drives the stop valve back, and the pneumatic grippers place the flux-coated stop valve back on the placement rod of the rotating mechanism. (4) Cover the protective cap. The rotating mechanism rotates and drives the shut-off valve coated with flux in step (3) to enter the protective cap covering station. The first cylinder on the protective cap covering station works and drives the round rod to extend forward and push against the protective cap on the copper pipe, flipping the protective cap to cover the port of the copper pipe. (5) First preheating, the rotating mechanism rotates and drives the stop valve with the protective cap on in step (4) to enter the first preheating station. The heating gun on the first preheating station heats the welding end of the stop valve for a period of time. (6) Secondary preheating: The rotating mechanism rotates to drive the shut-off valve that has undergone one preheating in step (5) to enter the second preheating station. The heating gun on the second preheating station heats the welding end of the shut-off valve for a period of time. (7) Welding: The rotating mechanism rotates and drives the stop valve that has been preheated twice in step (6) to enter the welding station. The welding machine at the welding station welds the welding end of the stop valve so that the copper pipe is welded and fixed to the welding end of the stop valve. (8) Air cooling: The rotating mechanism rotates and drives the shut-off valve that was welded in step (7) into the air cooling station, where it is naturally cooled for a period of time. (9) First air cooling, the rotating mechanism rotates and drives the air-cooled shut-off valve in step (8) to enter the first air cooling station. The air nozzle on the first air cooling station blows air onto the welded end of the shut-off valve for a period of time to help it cool down. (10) Secondary air cooling: The rotating mechanism rotates and drives the shut-off valve that has passed through the first air cooling in step (9) to enter the second air cooling station. The air nozzle on the second air cooling station blows air onto the welded end of the shut-off valve for a period of time to help it cool down. (11) Open the protective cap. The rotating mechanism works and drives the shut-off valve that has been cooled twice in step (10) to enter the vicinity of the protective cap opening mechanism. The first cylinder on the protective cap opening mechanism works and drives the round rod to extend forward and push against the protective cap covering the copper pipe end, flipping the protective cap away from the copper pipe end. (12) Water cooling, the rotating mechanism rotates to drive the stop valve of the copper pipe port protection cap opened in step (11) to enter the water cooling station. The nozzle on the water cooling station sprays cooling water onto the stop valve to help it cool, but do not let the cooling water come into contact with the welding end. (13) Unloading: The rotating mechanism stops when the water-cooled shut-off valve from step (12) approaches the unloading mechanism. The unloading mechanism uses pneumatic grippers to pick up the water-cooled shut-off valve from step (12) on the placement rod of the rotating mechanism, and then places the shut-off valve on the third conveyor belt. One assistant worker performs a visual inspection of the shut-off valve on the third conveyor belt and neatly arranges the qualified shut-off valves in the product box.

2. The welding gate valve method using a gate valve welding production line according to claim 1, characterized in that: In step (2), when the worker inserts the copper pipe into the welding end of the shut-off valve, it is necessary to ensure that the copper pipe is inserted into the bottom of the welding end.

3. The welding gate valve method using a gate valve welding production line according to claim 1, characterized in that: In step (3), the flux is an acid-free flux FB403L.

4. The welding gate valve method using a gate valve welding production line according to claim 1, characterized in that: In step (3), the flux is applied at a position of 0-10mm above the copper tube on the mounting plate.

5. A welding gate valve method using a gate valve welding production line according to claim 1, characterized in that: In step (5), the heating temperature for the first preheating is 550-620℃ and the heating time is 1.9-3.2s.

6. A welding gate valve method using a gate valve welding production line according to claim 1, characterized in that: In step (6), the heating temperature for the second preheating is 630-650℃ and the heating time is 1.9-3.2s.

7. A welding gate valve method using a gate valve welding production line according to claim 1, characterized in that: In step (7), the distance between the wire feed nozzle of the welding machine and the copper tube is kept at 10-15 mm.

8. A welding gate valve method using a gate valve welding production line according to claim 1, characterized in that: In step (7), the welding temperature is 650-740℃ and the welding time is 1.9-3.2s.

9. A method for welding gate valves using a gate valve welding production line according to claim 1, characterized in that: In step (8), the air cooling time is 3.2 to 3.8 seconds; in step (9), the temperature of the first air cooling is 400 to 440°C and the first air cooling time is 3.2 to 3.8 seconds; in step (10), the temperature of the second air cooling is 280 to 320°C and the second air cooling time is 3.2 to 3.8 seconds; in step (12), the temperature of the water cooling is 35 to 45°C and the water cooling time is 3.2 to 3.8 seconds.

10. A method for welding gate valves using a gate valve welding production line according to claim 1, characterized in that: Straight copper tubes must undergo the processing steps in steps (4) and (11); bent copper tubes do not need to undergo the processing steps in steps (4) and (11).

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